The leading search engines, such as Google, Bing and Yahoo!, use crawlers to find pages for their algorithmic search results. Pages that are linked from other search engine indexed pages do not need to be submitted because they are found automatically. Two major directories, the Yahoo Directory and DMOZ, both require manual submission and human editorial review.  Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for free to ensure that all pages are found, especially pages that are not discoverable by automatically following links  in addition to their URL submission console.  Yahoo! formerly operated a paid submission service that guaranteed crawling for a cost per click;  this was discontinued in 2009. 
Search engine crawlers may look at a number of different factors when crawling a site. Not every page is indexed by the search engines. Distance of pages from the root directory of a site may also be a factor in whether or not pages get crawled. 
What is SEO and why do you need it?
Search engine optimization ( SEO ) is the process of affecting the visibility of a website or a web page in a web search engine 's unpaid results — often referred to as "natural," " organic ," or "earned" results. In general, the earlier (or higher ranked on the search results page), and more frequently a site appears in the search results list, the more visitors it will receive from the search engine's users, and these visitors can be converted into customers.  SEO may target different kinds of search, including image search , local search , video search , academic search ,  news search and industry-specific vertical search engines.
So after you have that new website it's important that it generates "hits" and can be found on most of the major search engines, Google, Yahoo, Bing just to mention a few. New websites that we do include SEO optimizations with the base package. If you have a site already that you need optimized we can do that to ! Give us a call and discuss your options.
Webmasters and content providers began optimizing sites for search engines in the mid-1990s, as the first search engines were cataloging the early Web . Initially, all webmasters needed to do was to submit the address of a page, or URL , to the various engines which would send a " spider " to "crawl" that page, extract links to other pages from it, and return information found on the page to be indexed .  The process involves a search engine spider downloading a page and storing it on the search engine's own server, where a second program, known as an indexer , extracts various information about the page, such as the words it contains and where these are located, as well as any weight for specific words, and all links the page contains, which are then placed into a scheduler for crawling at a later date.
Site owners started to recognize the value of having their sites highly ranked and visible in search engine results, creating an opportunity for both white hat and black hat SEO practitioners. According to industry analyst Danny Sullivan, the phrase "search engine optimization" probably came into use in 1997. Sullivan credits Bruce Clay as being one of the first people to popularize the term.  On May 2, 2007,  Jason Gambert attempted to trademark the term SEO by convincing the Trademark Office in Arizona  that SEO is a "process" involving manipulation of keywords, and not a "marketing service."
Thanks Wikipedia for some of the above content. https://en.wikipedia.org/wiki/Search_engine_optimization